Langley Research Center (LaRC) in Hampton, Va., a ficility of the National Aeronautics and Space Administration (NASA), has employed flight simulation to support engineering research for at least 35 years. The vehicles most often studied are aircraft and spacecraft, but occasionally the facility is used to study more exotic systems such as trains, particle beams, flow control in wind tunnels, and aircraft landing carriages. The research engineer is usually testing a new or improved design in the area of automatic or augmented control, handling qualities, guidance, navigation, flight management, terminal air traffic management, air combat tactics or some combination of these. Different unrelated simulations are run simutaneously and the same simulation equipment may be used in sequential three-hour periods throughout the day to support different independent studies.
Recently, it was decided to replace the old equipment at LaRC by a design developed around a high-speed network technology called Computer Automated Measurement and Control (CAMAC). This network technology was developed by, and is widely used by, investigators in the particle accelerator field. It has many laudable features, not the least of which is that it conforms to a national and international standard. CAMAC, as used at LaRC, has two major components: an addressable, powered electronic chassis called a Crate with a backplane bus called a Dataway; and a ring master-slave network called a Highway which connects crates to the mainframe computer. The highway has a clock rate of five bytes per microsecond and a maximum useable data rate of three bytes per microsecond, but it uses very little handshaking protocol, does not block buffer data within the network, and does not compete (bus contention) for network services.
With this new design, it is necessary to have a clock system to synchronize simulations so as to obtain maximum utility from the equipment. This synchronization is necessary both to preserve the illusion of reality for the pilots and to permit rigid scheduling of demanding simultaneous applications.
It is therefore the primary object of this invention to provide a clock system for the synchronization of computations in a system that has a central computer and several remote sites that utilize the computer.
Other objects and advantages of this invention will become apparent hereinafter in the specifications and drawings.